If for some reason the Modality was unable to create the MPPS SOP Instance, another system may wish to perform this service. This system must make sure that the created PPS SOP Instance is consistent with the related Image SOP Instances.
Depending on the availability and correctness of values for the Attributes in the Image SOP Instances, these values may be copied into the MPPS SOP Instance, or they may have to be coerced, e.g. if they are not consistent with corresponding values available from the IS.
For example, if the MPPS SOP Instance UID is already available in the Image SOP Instance (in the Referenced Performed Procedure Step Sequence), it may be utilized to N-CREATE the MPPS SOP Instance. If not available, a new MPPS SOP Instance UID may be generated and used to N-CREATE the MPPS SOP Instance. In this case there may be no MPPS SOP Instance UID in the Referenced Performed Procedure Step Sequence in the corresponding Image SOP Instances. An update of the Image SOP Instances will restore the consistency, but this is not required.